Tone intensity envelope control for electrical musical instruments



Aug. 26, 1958 J. M. HANERT 2,843,919

7 I TONE INTENSITY ENVELOPE CONTROL FOR ELECTRICAL MUSICAL INSTRUMENTSFiled May 29. 1953 PlANO SUSTANING PEDAL.

KNEE 56y CONTROL QPERATD WHENEVERANY PEDAL IO [5 DEPRESSED g 4 M H t.the tuning circuit.

tes Patent TONE INTENSITY ENVELOPE CONTROL FOR ELECTIRHCAL MUSICALINSTRUIVIENTS John M. Hanert, Des Plaines, llL, assignor to HammondOrgan Company, a corporation of Delaware Application May 29, 1953,Serial No. 358,517

9 Claims. in. sit-1.26

al. Patent No. 2,480,132, granted August 30, 1949, which discloses apedal-controlled instrument for use with a piano for producingpercussive accompaniment bass tones. In the instrument shown in saidpatent, the initial intensity of the tones produced was determined bythe velocity of pedal depression. Thus, when a loud tone was to besounded, the player had to tap the pedal very sharply to obtain thenecessary high velocity of pedal depression. This resulted inundesirable noise due to the contact of the sole of the players shoewith the pedal. Furthermore, the player had to acquire a new technique,that is, the ability to strike the pedals with the velocity required toobtain a tone of the desired intensity.

It is an object of the present invention to provide an intensity controlwhich is not dependent upon the velocity of pedal depression but inwhich the desirable sharp attack and slow decay characteristics of thetonal envelope inherent in the instrument of said patent are retained.

A further object is to provide an improved intensity control for apedal-operated accompaniment instrument which is elfective only when allpedals are released. In other words, the control is adjusted prior tothe depression of a pedal and any changes in its position of adjustmentwhile a pedal is depressed are ineffective to alter the percussiveintensity envelope of the tone being pro,- duced.

Other objects will appear from the following description, referencebeing had to the accompanying drawing which is a block and schematiccircuit diagram :of the instrument.

The instrument is played by twelve pedals 10 for an octave of notes inthe bass register. Each of these pedals, except that for the note C,opens a switch 12 upon depression of the pedal. The switches 12 areconnected in series in the tuning circuit of a push-pull oscillator 14,

the tuning circuit including an inductance L16, the terminals of whichare respectively connected to the control grids of triodes13 and 19. Thetuning circuit also includes one or more capacitors C20 connected inparallel across the terminals of the inductances L16, the numberdepending upon which of the pedals 10 is played. It will be noted thatthe capacitor C20 associated with the pedal 10 for the note B is at alltimes elfcctive in The values of the capacitors C20 are such that theoscillator 14 will be tuned to a frequency corresponding to the pitch ofthe operated pedal, and

when none of the pedals is operated will be tuned to the it open untilanother pedal 10 is operated, as shown in the aforesaid patent.

The oscillator 14 is of known construction and is mere- 1yrepresentative of a large variety of well-known types of oscillators orother bass tone signal generators which could be used. The output of theoscillator 14 is supplied to a distorter 22 which may be of anywell-known construction and may include a pair of triodes 23 which arebiased so that only the positive peaks of their input signals aretransmitted. The output signals are thus in the form of pulses which arerich in harmonic content. When converted into sound, this signalproduces very desirable bass tones of quality similar to those of a richpiano bass tone sounded with its octave. The octave effect is obtaineddue to the use of an attenuating capacitor C23 in the output circuit ofone of the triodes 23.

The output of distorter 22 is supplied to the control grid 24 of acontrol pentode 26 through a circuit including blocking capacitors C28and C29 in series. The connection between these two capacitors isconnected to a 58 v. terminal by a high value resistor R30 to preventthe build-up of static charges on these capacitors. The suppressor grid32 is connected to the cathode 34, and the latter is connected to groundby a low value resistor R36. The plate 38 is connected to a source ofplate voltage shown as a terminal +280 v. through a load resistor R40.The screen grid 42 has its potential determined by a voltage dividernetwork connected between the +280 v. terminal and ground and includingresistors R44, R46, and a potentiometer R48. The junction betweenresistors R44 and R46 is connected to the screen grid and thepotentiometer R48 is adjusted so that a given voltage such as 58 v. onthe control grid 24 will bias the pentode as closely as possible tocutolf. The pentode 26 is of the remote cutofi type such as a 6SK7 tube.The plate 38 is connected by conductor 50, capacitor C52, a minimumvolume control potentiometer R54, and a capacitor CS6, to the controlgrid 58 of an amplifying triode 60. The potentiometer R54 is connectedto ground through a resistor R62 in series therewith and is operated bya suitable volume control knob adjustable at will by the player of theinstrument.

The triode 60 operates in the manner of a cathode follower, -or phasesplitter and its output circuits are respectively coupled to controlgrids of power amplifying tetrodes 64, 65, the outputs of which aretransformer coupled to a pair of speakers 68 connected in parallel.

A conductor 70 connects the control grid 24 of control pentode 26 withone terminal of a resistor R72, the other terminal of which is connectedto ground through a capacitor C74 and to a 58 v. terminal through aresistor R78. Resistor R72 is also connected through a resistor R to acontact 82 of a single pole double throw switch having a movable contactarm 84. The switch arm 84 is connected to a -58 v. terminal through aresistor R86 and is connected to ground through a capacitor C88. Theother switch contact 90, with which the switch arm 84 is normally incontact, is connected to ground through a conductor 92 and a resistorR94 constituting with R86 a part of a voltage dividing networkdetermining the voltage to which the capacitor C88 is normally charged.Other parts of this network comprises a group of resistors R to R107,each of which has one terminal connected to conductor 92 and its otherterminal connected to one of a group of switch contacts 110. Thecontacts are adapted to be engaged cumulatively in succession and makeelectrical contact with a contactor 112, diagrammatically illustrated asa curved blade pivoted at 114. An insulating handle lever is secured tothe blade 112 and the blade and handle are normally urged clockwise by asuitably anchored coil spring 118. The blade 112 is connected to themovable contact of a potentiometer R122 which, in series with limitingresistors R124 and R125, is connected between ground and a 58 v. termi-3 nal. The contact 120 will usually be adjusted to a position at whichthe potential is about 40 v.

The switch arm 84 is moved to its dotted line position by suitablemechanical means (for example, as disclosed in the aforesaid Patent No.2,480,132) whenever any of the pedals is depressed, and is springreturned upon release of the pedal. Depression of any pedal also opens aswitch 126 which is connected in series with a switch 128 and a resistorR130 between a 58 v. terminal and the switch contact 82. The switch 128is opened by depression of the sustaining pedal 129 of the piano withwhich the instrument is being played.

In playing the instrument, the handle 116, which may be in position tobe operated by the knee, is moved countterclockwise for increasedloudness and permitted to be moved clockwise by spring 118 for decreasedloudness.

The potentiometer R122 is normally not adjusted by the player and may beset by the manufacturer of the instrument at a value such that areasonable minimum of intensity of sound is produced when the blade 112is in contact with the contact 110 which is directly connected to theconductor 92. As the knee operated control handle 116 is moved clockwiseor counterclockwise from an intermediate position, more or fewer of theresistors R100 to R107 will be effective to determine the voltage acrosscapacitor C88.

The resistors R100 to R107 are of such values that as they aresuccessively and cumulatively effective in the voltage divider circuitthey will cause the intensity of the tones produced to decrease inlogarithmic steps of loudness. In other words, their values aredetermined in a large part by the grid bias-plate currentcharacteristics of the pentode 26.

The pentode 26 is normally biased to cutoff because its grid 24 isconnected through conductor 70 and resistors R72 and R78 to a 58 v.terminal.

In addition to operating the switch arm 84, each pedal 10 upondepression opens a switch 126 one pole of which is connected to a 58 v.terminal and the other pole of which is connected to a switch 128adapted to be opened whenever the sustaining pedal 129 of the piano isheld down. A resistor 130 connects the switch 128 to resistor R80.

When any of the pedals 10 is depressed, it first operates to open itsassociated switch 12 and thus tune the oscillator 14 to the pitch of thenote corresponding to the pedal, and thereafter to move switches 84 and126 to their dotted line positions.

When switch 84 engages contact 82, a portion of the charge on capacitorC88 will be transferred to capacitors C74 and C29. Capacitor C88 has avalue approximately twenty times as great as that of capacitor C74, andits "associated resistor R86 has a value approximately one twentieth asgreat as that of R78 so that the time constant of the mesh C88, R86, isapproximately equal to that of the mesh C7 4, R78. Because the capacitorC88 is so much larger than the capacitor C74, the latter will be chargedto the same voltage as that across C88 nearly instantly, the rate ofcharge being determined mainly by the low value resistor R80.

The charges across capacitors C74 and C88 are reduced by current flowthrough the resistor R72 and conductor 70 to capacitor C29 and to thecontrol grid 24 of pentode 26. The values of the resistors andcapacitors are such that the intensity envelope will be a curve havingan initial concave slowly rising portion followed by a rapidly risingconvex portion to a point of maximum intensity. Thereafter, thecapacitors C74 and C88 will be discharged primarily through theirassociated resistors R78 and R86 so that the potential on the controlgrid 24 will decrease exponentially in the manner of the discharge curveof a capacitor in a circuit of substantial resistance.

In playing the instrument the knee operated lever 116 is swung back andforth to control the intensity of the tones produced. If any pedal isheld depressed while moving of the lever 116 it will be clear that suchmovement of the lever cannot have any effect on the bias potentialapplied to the control grid of the control pentode because the switcharm 84 is not in engagement with contact 90. It will likewise be clearthat movement of the lever 116 cannot have any eifect on the acousticoutput while none of the pedals is depressed. In this respect, the lever116 and voltage dividing network associated therewith function in anentirely different manner than conventional volume controls. It is onlyat the instant that a pedal is depressed that the position of thecontrol lever 116 has any effect or significance. The control lever 116and associated voltage dividing network is thus a means forpredetermining the intensity of the tone to be produced upon thedepression of any pedal. Thereafter, the intensity envelope of the tonesounded is determined by the time constant of the circuit which includesthe following elements, R86, C88, switch 82-434, R80, R78, C74, R72, andC29. When the pedal is released the capacitor C74 is rapidly dischargedthrough a relatively low resistance circuit including resistors R and Rand switches 126 and 128. However, if the sustaining pedal 129 isdepressed at the time that one of the pedals 10 is released this lowresistance circuit for the discharge of the capacitor C74 is open. Theintensity of the envelope of the tone will thus have a decay portiondetermined mainly by the time constant of the capacitor C74 and resistorR78. From the foregoing it will appear that irrespective of the positionof the control lever 116 the intensity envelope of the tone producedupon depression of one of the pedals 10 will have an attack portion freefrom objectionable transients and a decay portion which will be long ifthe pedal is held depressed for a long period or if the sustaining pedal129 of the piano is depressed before the pedal 10 is released.

Inasmuch as the values of a number of the components of the intensityenvelope control circuit are of importance in obtaining the desiredresults, exemplary values of these components are set forth below, itbeing understood that most of these values are not critical and thatsubstantial changes could be made in the values of many of thecomponents without greatly affecting the results obtained, especially ifcompensating changes were made in the values of other components. Thevalues given are under the assumption that the pentode 26 is of the 6SK7type.

While I have shown and described a particular embodiment of myinvention, it will be apparent to those skilled in the art that numerousmodifications and variations may be made in the form of constructionthereof, without departing from the more fundamental principles of theinvention. I therefore desire, by the following claims, to includewithin the scope of my invention all such Similar talents played inconjunction with a piano having a sustaining pedal, the combination of aplurality of playing keys, tone signal generating means, an amplifierfor the signals supplied by the generating means, said amplifier havinga terminal the potential of which determines the amplitude of the outputsignal, an electroacoustic transducer connected to the output of theamplifier, means operable by the keys to determine the pitch of the tonesignal supplied to the amplifier by the generating means, a potentialsource of such value that when applied to the terminal will cut oil theamplifier, a voltage source of such value that when applied to saidterminal will cause the amplifier to amplify the tone signals to themaximum desired extent, a first capacitor connected between the saidvoltage source and said terminal, a first resistor connected betweensaid potential source and said terminal, a single pole double throwswitch biased so as to have its movable element normally engaging onecontact thereof, means to apply an adjustable potential to said switchcontact, a second resistor connecting the movable switch element-to saidpotential source, a second capacitor connecting said movable switchelement to the voltage source, a conductor connecting the other contactof said switch to said terminal, and means for operating said switchagainst its bias upon operation of any of the playing keys.

2. The combination set forth in claim 1 in which the time constant ofthe first capacitor and first resistor is substantially the same as thetime constant of the second capacitor and second resistor.

3. The combination set forth in claim 2 in which there is a switchoperable by the sustaining pedal of the piano, in which said switch isconnected between the terminal and the potential source, and in whichmeans are provided to disconnect the sustaining pedal operated switchfrom the potential source whenever any of the playing keys is depressed.

4. In an electrical musical instrument having a control pentode having acontrol grid the bias on which determines the loudness of the tone to beproduced, means for controlling the bias on said grid comprising asource of bias potential of such value that when applied to said gridwill cause the pentode to be biased beyond cutoff, a pair of resistorsin series connecting said source to the control grid, a capacitorconnected between the junction of said resistors and a point of fixedpotential substantially higher than that of said source, a thirdresistor and second capacitor connected in series between said point offixed potential and said source, a voltage divider connected betweensaid point of fixed potential and said source and having an outputterminal, a control for adjusting said voltage divider to vary thevoltage at said output terminal, a conductor including a switchconnecting said terminal to the junction between said third resistor andsecond capacitor thereby to charge said second capacitor to a potentialdetermined by the position of said control, and a circuit including saidswitch to connect said junction to said first capacitor.

5. In an electrical musical instrument having an output system includinga terminal the potential of which determines the intensity of the toneproduced, a first capacitor connected between said terminal and a pointof fixed potential, a second capacitor of value much greater than thatof the first capacitor, adjustable potential means for charging saidsecond capacitor, resistance means respectively connecting said firstand second capacitors to points of fixed potential of such value as toprevent transmission of signals through the output system when appliedto said terminal, said capacitors and their respective resistance meanshaving substantially the same time constants, and means operable by theplayer for dis connecting the second capacitor from its charging meansand connecting it effectively in parallel with the first capacitor,whereby the first capacitor will have impressed across it a potentialnearly as great as that of the initial potential of the second capacitorand the potential on the two capacitors will decrease at substantiallythe same rate to produce gradual decay in the intensity of thetransmitted signal.

6. A tone intensity envelope control for an electrical musicalinstrument having an amplifier provided with a terminal the potential ofwhich determines the amplitude of its output signal, tone signalgenerating means, a sustaining pedal, and playing keys for determiningthe pitch of the tone signals supplied by the generating means to theamplifier, the combination of a first mesh including a first capacitorconnected to said terminal and normally applying a cutoff potentialthereto, a second mesh including a second capacitor of value muchgreater than that of the first capacitor, said first and second mesheshaving substantially equal time constants, adjustable potential meansnormally connected to said second capacitor to maintain a potential uponthe capacitor of such value that when applied to said terminal willcause the tone signals to be amplified, means operable by any of theplaying keys to disconnect the second capacitor from the adjustablepotential means and thereafter to connect the second capacitor to saidterminal, and a low impedance circuit connected to said first capacitorfor rapidly discharging the latter, said circuit including a switchoperated upon depression of any of the playing keys and a switchoperated upon depression of the sustaining pedal.

7. In an electrical musical instrument for producing musical toneshaving percussion tone intensity envelopes, the combination of aplurality of playing keys, tone signal generating means, a variable gaincontrol device for the signals supplied by the generating means, saiddevice having a terminal the potential of which determines the amplitudeof the signal supplied to the output system, an electroacoustictransducer connected to the output of the amplifier, means operable bythe keys to determine the pitch of the tone signal supplied to theamplifier by the generating means, an adjustable potential source, anexpression control operable by the player during the course of renderinga musical selection to adjust the potential of said source, a capacitor,means normally connecting said capacitor to the adjustable potentialsource, and means operable upon operating any of the playing keys todisconnect said capacitor from said adjustable potential source andimmediately thereafter to connect said capacitor to said amplifierterminal, whereby the intensity of the tone to be sounded ispredetermined by the adjustment of said adjustable expression control.

8. In an electrical musical instrument for the production of toneshaving percussion intensity envelopes, the combination of a plurality ofplaying keys, tone signal generating means, a variable gain controldevice for the signals supplied by the generating means, said devicehaving a terminal the potential of which determines the amplitude of itssignal output, an electroacoustic transducer coupled to the output ofthe device, means operable by the keys to determine the pitch of thetone signal supplied to the amplifier by the generating means, a firstcapacitor, a second capacitor, the capacitance of said first capacitorbeing at least twice that of said second capacitor, a first resistorconnecting said first capacitor to a point of fixed potential, a secondresistor connecting said second capacitor to a point of fixed potential,the values of said resistors being proportioned so that the timeconstant of said first capacitor and resistor corresponds substantiallyto that of said second capacitor and resistor, a connection between saidsecond capacitor and the terminal of said control device, means forcharging said first capacitor to a potential of value such that whenapplied to said terminal will cause eflicient transmission of thesignal, and key operated means for disconnecting said first capacitorfrom its charging means and to connect it to the second capacitorthereby to impress upon the said second capacitor a voltagesubstantially greater than half of that on the first capacitor at theinstant that the latter is connected to the second capacitor, wherebythe residual potential on said second capacitor plays a relativelyunimportant role in the po' tential applied to the terminal of thecontrol device upon quickly repeated operation of the keys.

9. In an electrical musical instrument, the combination of means forgenerating electrical tone signals of pitches corresponding to those ofa musical scale, an output system, a plurality of depressible playingkeys and means operable thereby to cause transmission from thegenerating system to the output system of a pitch related to the keywhich is depressed, an electro acoustical translating means forming partof the output system, an intensity envelope control means forming partof the output system, an expression control means adjustable by theplayer to predetermine the initial in- 20 tensity of the tone signalstransmitted through the output system, and means operable upondepression of a playing key to transmit from the expression controlmeans to the intensity envelope control means a setting corresponding tothat of the position of the expression control means and at the sametime to disconnect the expression control means from the intensityenvelope control means, whereby the expression control means may beadjusted while a playing key is being held depressed and that uponrelease of the depressed playing key and upon depression of the same oranother key the expression control means is effcctive to set saidintensity envelope control means to cause initial intensity of a tonesignal transmitted 'by the output system to be responsive to theprevious setting of the expression control means.

References Cited in the file of this patent UNITED STATES PATENTS2,276,390 Hanert Mar. 17, 1942 2,432,152 Hanert Dec. 9, 1947 2,482,548Kerkhof Sept. 20, 1949

